Project Information

Location: Wilmington, Vermont

Project Type: Municipal Wastewater Treatment - Primary BOD & TSS Removal

Completion Date: April 2016

Treatment Objectives

Design Flow:
1,280 m3/day (0.338 MGD)

Effluent Total Phosphorus:
TSS: 80 mg/L (60% Removal)
BOD: 210 mg/L (30% Removal)


Project Background & Challenges

A variety of factors can cause engineers to rethink capacity expansion when it comes to getting more out of your wastewater treatment plant (WWTP). These can include anything from physical footprint and costs, all the way to the level of treatment desired and power demands for operations. On a very basic level, the simple matter of real estate can make or break the feasibility of a wastewater solution that is both effective and economical.

The town of Wilmington can be found in Windham County, Vermont, at the heart of the southern Vermont snowbelt. This snowbelt lies mainly within the southern Vermont portion of the Green Mountain National Forest and includes the high elevation Southern Vermont towns of Woodford, Searsburg, Malboro and Wilmington.

The WWTP in Wilmington was looking to reduce Total Suspended Solids (TSS) by 60% and Biochemical Oxygen Demand (BOD) by 30% in order to meet incoming water quality regulalations. However, in order to meet these objectives, they faced challenges in terms of both space and budget.

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The Nexom Answer

After exploring options, the engineers in WIlmington turned to EcoBELT™, a rotating belt filter that offers small-footprint primary treatment and allowed the WWTP to expand primary clarification and reduce BOD loading to the secondary system by 20-40% and Total Suspended Solids (TSS) by 30-80%.

Engineers around the world have found rotating belt filters to be an efficient and economical solution to a variety of wastewater challenges due to its flexibility to be arranged in multiple configurations. In new plants, the EcoBELT replaces conventional primary clarification. In existing plants, these filters are integrated to expand primary clarification, as well as relieve solids and BOD loading to the secondary system. By removing this loading from the front end, you automatically improve the performance of secondary and tertiary processes.

Engineers have been able to maximize the use of existing infrastructure while expanding plant capacities by installing the EcoBELT and thus reallocating the capacity of conventional clarifiers to the secondary system. In addition to the flexibility and ancillary plant benefits, the EcoBELT is less than one-fifth of the lifecycle cost of conventional treatment technologies.

The EcoBELT also offers an optional, fully-automated hot water wash to flush fats, oils and greases that accumulate over time, and EcoBELT’s reliable solids dewatering capability also means loading isn’t just diverted, it falls into a dumpster to be disposed of through landfilling, as illustrated by the image at left.

Site Construction

Upgraded System Performance

The initial performance test for the Wilmington WWTP’s EcoBELT unit took place in March 2016 immediately after start-up and lasted for part of one day.

Seven manual grabs of 1 liter each were composited and then split into three separate samples for lab analysis for both Influent and Effluent to verify compliance with the basis of design. A single grab was used for measuring the total solids content of the discharged solids cake. All samples were then delivered to EAI Labs in Keene, NH for analysis.

At the beginning of the performance test, Nexom tested the unit’s ability to handle maximum flow capacity. In order to accomplish this, the lead pump was disabled for the EcoBELT feed. Once the level in the holding tank reached a high level the lag pump automatically started at 100% until the level in the tank reached the high flow shutoff point. This provided enough flow time to verify that the belt mesh selection allowed enough throughput to reach the unit’s flow targets.

Following extensive testing, the EcoBELT installed at the WWTP in Wilmington has satisfied the flow capacity requirements of 235 GPM with a peak measurement of 265 GPM.

Additionally, it satisfied the BOD removal requirements of the specified design with an average removal of 50.7%, and the TSS removal requirements of the specified design at >60% removal.